| Particulate reinforced metal matrix composites possess several additional advantages such as light weight, high specific strength and stiffness, wear-resisting and high temperature-resisting. So they are widely used in many general applications in spaceflight, electronic industries, car manufacturing and so on. According to the difference of the reinforcer's formation, the composite's manufacturing methods can be divided into traditional way and in situ way. The advantage of the traditional way is the simple processing but the particles can be polluted easily. In situ way has the advantages that the reinforcer is formed in the matrix. The paticles are fine and clean, and can bond well with the matrix.A new idea to fabricate aluminum matrix composites by combined in situ particle strengthening and stirring cast by adding NH4Al(SO4)2 which is the raw materials for fabricating commercial high-purity superfine Al2O3 to aluminum melt had been proposed. The NH4Al(SO4)2 decomposed at the temperature of 900℃.2NH4Al(SO4)2 = Al2(SO4)3 + 2NH3↑+ SO3↑+ H2O↑The Al2O3 particles yield by the decomposition could distribute well into aluminum melt. Compared with the traditional ways, the way of fabricate aluminum matrix composites by adding NH4Al(SO4)2 to Al melt possesses several advantages such as the Al2O3 particles which are generated by the decomposition of NH4Al(SO4)2 in Al melt are fine and clean and bond well with the matrix. NH4Al(SO4)2 can decompose completely and there is no substance left to affect the element of the matrix. At the same time, the SO3 yielded from the decomposition of NH4Al(SO4)2 can react with aluminum to increase the quantity of Al2O3.The processing conditions of fabricating aluminum matrix composites by combined in situ particle strengthening and stirring cast by adding NH4Al(SO4)2 to Al melt had been studied. The processing is: keeping the melt at the temperature of 900℃ and the velocity of stirring at 350400r/min, putting the NH4Al(SO4)2 powder mixed with same... |
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